This invention relates to a transmission mechanism for imparting rotational movements to a driven member by means of a reciprocating drive member. Such rotational movements may be continuous, but preferably they are of a reciprocating type suitable for controlling valves, the driven member then being a shaft for rotating the valve.
By the U.S. Pat. No. 1,929,268 such a transmission mechanism is previously known comprising means pivotally connected to the drive member for alternately actuating two dogs of an operating unit associated with the driven member--the dogs being located on either side of a central plane through the travel path of the drive member--so as to move the operating unit to one or the other of two end positions, thereby providing the rotational movement of the driven member.
This mechanism might be sufficient for controlling valves of the type presented in said patent specification, i.e. valves being rotated an angle merely amounting to about 20.degree. to 30.degree.. When controlling other types of valves, such as ball valves, throttle valves or the like, it is, however, necessary to rotate a shaft at least 90.degree. to and fro between the end positions thereof. In connection with the latter valves, the transmission mechanism according to U.S. Pat. No. 1,929,268 is quite impossible to use. Furthermore, the mechanism in question is rather complicated and unreliable.